Cavities are areas of decayed tooth enamel (or, if they’re especially deep, dentin), and we typically treat the cavities with a filling. We remove the decayed and softened tooth material and replace it with synthetic material that is immune to decay.
But the problem with fillings is that they can be vulnerable to secondary decay. Secondary decay is when oral bacteria and food accumulating around a filling cause decay that penetrates the tooth right next to the filling. This is particularly common with metal amalgam fillings, but it can occur with all fillings. When secondary decay occurs, it can significantly weaken the tooth, requiring a dental crown to restore, and it may even penetrate into the tooth nerve, requiring a root canal procedure.
Now researchers think they might have a new weapon to help protect against secondary decay: bioactive glass.
Bioactive glass gets its name from the fact that it’s made of silicon (like glass) but contains trace chemicals that help it to bond to bone. This type of material was originally developed in the 1960s, and came to be applied in bone grafts, such as those around dental implants, and elsewhere.
But it wasn’t until the 1990s that researchers came to appreciate the antibacterial properties of bioactive glass. That’s when they realized that it could suppress the growth of common oral bacteria such as Streptococcus mutans and bacteria that caused serious gum disease, such as Porphyromonas gingivalis.
And now researchers are hoping to take advantage of those properties to make fillings that resist secondary decay.
One of the goals is to make sure that bacteria couldn’t penetrate into the space around fillings. To test this, researchers used extracted human molars that were treated with fillings. The fillings were either normal composite fillings or they were composite fillings that included bioactive glass. These teeth were then infected with S. mutans and inserted into a machine that simulated chewing for two weeks (my jaw gets sore just thinking about it!).
When they examined the fillings they found that the bioactive glass had indeed made a big difference. Where bacteria was able to penetrate fully into teeth with normal composites, they were only able to get an average of 61% of the way into the space around fillings with bioactive glass.
This is a promising finding. It doesn’t definitely establish that bioactive glass could protect us from secondary decay, but it does make us think that this could be the material of choice for future fillings.